Chromatography

Question 1

Describe how you would use chromatography to separate out photosynthesis pigments from a leaf extract (3 marks)

Answer 1

• Draw an origin line at the bottom of the chromatogram
• Place concentrated spot of extract on the origin line
• Place chromatogram into the solvent with the origin line above the solvent
• Allow time to run then remove from solvent and mark the solvent font

Question 2

Why draw origin in pencil, not pen

Answer 2

Pigment molecules in ink will dissolve in solvent and mix with the pigments from the extract

Question 3

Why do pigment molecules separate

Answer 3

Different molecules have different solubilities in the solvent

Question 4

What is the equation for the Rf value

Answer 4

distance moved by molecule / distance moved by solvent